1. Field of the Invention
This invention concerns a system for determining the concentration of a particular gas in a flowing stream of gases.
2. Description of the Prior Art
Energy is often produced by the combustion of fossil fuels, and the combustion process generates gases which are discharged through a stack to the atmosphere. The exhaust gases are normally a mixture of chemical compounds including, for example, carbon monoxide, carbon dioxide, sulphur dioxide, nitrogen oxide and other gases as well as solid particles. Regulatory agencies often require that no more than specified maximum quantities of the gases and particulates be discharged through the stack to the atmosphere. Consequently, to comply with such regulations, it is necessary to determine the concentration of particular combustion gases in the stream of gases in the stack.
There are known analyzers to measure the concentration of combustion gases in a stack. Before such analyzers can be used to achieve accurate results they must be calibrated. The calibration process can include introducing a series of gas samples into the analyzer while the analyzer is in operation and recording the output of the analyzer in response to each member of the series of samples. Utilizing the concentrations of a particular gas in the series of analyzed gases a graph is constructed depicting the relationship between the actual concentrations of the gas of interest and the output of the analyzer. Thus a person operating the analyzer can use the graph to determine the concentration of a particular gas in a sample which is analyzed based upon the output of the analyzer.
One major shortcoming of the calibration process described above is that it relies upon an operator's judgement to fit a curve to data points. This is frequently subject to error. Another shortcoming is that the graph can only be utilized by a person, and is not readily readable by a machine. Thus, values of the concentration determined from the graph are susceptible to error.